The instruction selection pass recognizes opportunities for using
combined arithmetic and logical operations and addressing modes
offered by the target processor. For instance, the expression x + 1
can take advantage of the "immediate add" instruction of the processor,
and on the PowerPC, the expression (x >> 6) & 0xFF can be turned
into a "rotate and mask" instruction.
Instruction selection proceeds by bottom-up rewriting over expressions.
The source language is Cminor and the target language is CminorSel.